A conventional method of manufacturing a thin stainless steel sheet employing a continuous casting process comprises casting a cast plate having a thickness of not less than 100 mm while the mold is vibrated in the casting direction, cleaning the surfaces of the cast plate, hot-rolling the cast plate into a hot strip of a thickness on the order of several millimeters by a hot strip mill consisting of roughing stands and finishing stands arranged in series, after heating the cast plate to a temperature not lower than 1000.degree. C., descaling the hot strip, if needed, after annealing the same, cold-rolling the descaled hot strip, and finish-annealing the cold-rolled strip.
Such a conventional method has problems in that a very long hot strip mill must be used for hot-rolling the cast plate of a thickness not less than 100 mm, and a large quantity of energy must be used for the specific gravity of the cast plate and rolling the cast plate.
To solve such problems, studies have been made to develop an improved continuous casting process capable of producing a cast plate having a thickness equal to or nearly equal to that of the hot strip. Synchronous continuous casting processes of a twin-roll system and a twin-belt system, in which the speed of the cast plate relative to the inner surface of the mold is zero, are reported in papers inserted in the special edition of "Tetsu to Hagane", '85-A197 -'85-A256.
In a first method employing the continuous casting process of a twin-roll system, a thin cast plate of a thickness in the range of 0.5 to 10 mm is produced. Then, a sheet of a desired thickness is produced only by cold-rolling after subjecting the cast plate to an annealing process and a pickling process for descaling.
In a second method employing the continuous casting process of a twin-roll system, a thin cast plate of a thickness in the range of 0.5 to 10 mm is produced. Then, the cast plate is hot-rolled to produce a hot-rolled strip, the hot-rolled strip is descaled by pickling, and then the descaled strip is cold-rolled in a sheet of a desired thickness.
The cast plate produced in accordance with the above prior methods has a coarse crystal grain microstructure and, then to produce a cold-rolled sheet of a satisfactory surface quality by rolling the cast plate, the draft of the cold-rolling process in the first method must be considerably large, and the second method requires that the cast plate be hot-rolled before the cold-rolling process. Accordingly, these previously proposed methods have problems a long processing time and a significant increase of the cost of the sheet.